From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36189EB64DA for ; Mon, 19 Jun 2023 12:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230058AbjFSMCe (ORCPT ); Mon, 19 Jun 2023 08:02:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37388 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbjFSMCc (ORCPT ); Mon, 19 Jun 2023 08:02:32 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C55A11D for ; Mon, 19 Jun 2023 05:02:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=qa+vS4eBLwHQzXvRvXGPmsksUe4kxzWk6YpXlGn9Oyk=; b=cklv7UXKujqrKzsZTk/OOs2rX9 Z3ByfDFcmcJ4n6tfsFtg2UP0Z0TOoB+/VKJzFazKm3XW8V/6nJdFLvyjVPE0Tg4+WkN1KjBGlB4YF RZszpFv8yYMQ7f+my/2KIQF3TlT5MgEUz1T9M3Hmy8hnS+9HjsOxXPnK12EdgEsORJzWQGZIB4E9I 8gr5hhpttMHFp3vGOswOdb1gDa4dCKlMnYiabZYILY/1yV33CjmaDGFE4VaiJzzmWD0cbzceGJei3 FlaHSVRKWEioC6ZnKcX7ZL+l+J6TeA7u0Rqw+PTZygh6EpJGRNbc2bYdXfcQlFlvkysOoBaLxKPLZ G2+xQ3cA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qBDaL-00EiUv-1s; Mon, 19 Jun 2023 12:02:18 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BCFEB300322; Mon, 19 Jun 2023 14:02:15 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A0FF6201AF169; Mon, 19 Jun 2023 14:02:15 +0200 (CEST) Date: Mon, 19 Jun 2023 14:02:15 +0200 From: Peter Zijlstra To: Daniel Bristot de Oliveira Cc: Joel Fernandes , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-kernel@vger.kernel.org, Luca Abeni , Tommaso Cucinotta , Thomas Gleixner , Vineeth Pillai , Shuah Khan Subject: Re: [RFC PATCH V3 6/6] sched/fair: Implement starvation monitor Message-ID: <20230619120215.GO38236@hirez.programming.kicks-ass.net> References: <841849b5-1f9c-4f0e-2de8-1da278256888@kernel.org> <20230616120507.GM83892@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230616120507.GM83892@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 16, 2023 at 02:05:07PM +0200, Peter Zijlstra wrote: > On Tue, Jun 13, 2023 at 03:41:30PM +0200, Daniel Bristot de Oliveira wrote: > > > In an 0-laxity scheduler, the server would run at 0-laxity, jumping in > > front of DL tasks... that would break EDF. It would be mixing two > > schedulers in one. It is not required and likely not a good idea either. > > I did consider a hybrid 0-laxity and EDF scheduler for mixed > criticality, as have others like Ted Baker IIRC. IIRC it can be done > using an augmented tree, but none of that solves the problems 0-laxity > has (like over preemption and the general problem of playing chicken by > doing things at the *VERY* last possible moment). > > I think I did a talk at OSPERT on this at some point many years ago. > Luckily some bright fellow had this semi-partitioned stuff that would > make live much simpler :-) I must clarify; I was thinking Least-Laxity-First, which is ofcourse not the same as a 0-laxity scheduler.